Revision and Updates to the Environmental Dredging Pilot Study Lower Passaic River Restoration Project

Transcription

1 Revision and Updates to the Environmental Dredging Pilot Study Lower Passaic River Restoration Project Project Delivery Team Meeting Project Delivery Team Meeting March 4, 2009

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4 Outline Design and Objectives of Pilot Study Revisions and Updates Volume of Sediments Dredged Productivity Analysis Resuspension Conclusion and Next Steps

5 Design & Objectives Pilot Study designed to examine production environmental dredging One mechanical dredging system equipped with an 8-CY clamshell bucket Evaluate productivity, vertical accuracy, and Best Management Practices ces Evaluate dredge-related resuspension through a monitoring program Three target depths over Evaluate approximately 1 acre of decontamination area in 5 work days technologies og es

6 Design & Objective Date December 5 December 6 December 7 December 8 December 9 December 10 Dredging gactivity 13-foot MLW cut 11-foot MLW cut 15-foot MLW cut 15-foot MLW cut No dredging due to storm 15-foot MLW cut

7 Pilot Study was NOT intended to report on. Other dredging performance features and technologies Other remedial alternatives such as capping Clean-up passes or residuals Material handling and decontamination technology (separate reports) Cost implications for a full-scale dredging operation Quality of life issues Feasibility study will extrapolate Pilot Study data to estimate a full scale operation

8 Revision on Volume of Sediments Dredged

9 Revision on Volume of Sediments Dredged Method 1 Method 2 Sum the daily dredge volumes by evaluating daily bathymetric surveys to the pre- dredge survey Compare the river bottom elevations before and after the dredging operation by using the predredge and post- dredge surveys

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11 Method 1 Pre-dredge Versus Post-dredge Survey 3,800 ±100 Cubic Yards

12 Method 2 Daily Survey Comparison 4,000 ±210 Cubic Yards

13 Revision on Volume of Sediments Dredged Date Malcolm Pirnie (Cubic Yards) Jay Cashman (Cubic Yards) December ± December 6 1,200 ±30 1,400 December ± December ± December ± Total Volume 4,000 ±210 4,200 * Values rounded to two significant figures

14 Revision of Productivity Analysis

15 Revision of Productivity Analysis Daily surveys were used to estimate productivity Revised work time breakdown based on ClamVision data for actual dredge time Linked cycle time (ClamVision data) to the work time analysis to separate equipment movement from dredge time

16 Revision of Productivity Analysis Evaluation decreased dredge time and increased equipment movement, which h will cause an increase in productivity. Parameter Draft Dredge Pilot Value Revised Value Average Dredging Time 6.2 hours 5.0 hours Average Working Day 11 hours 10.5 hours Work Day minus Client Standby 9.6 hours 9.2 hours

17 Revision on Productivity Analysis EQUIPMENT MOVEMENT 1.7 HOURS LOST TIME 0.9 HOURS DOWNTIME 0.1 HOURS OPERATING TIME 5 HOURS CLIENT- DIRECTED STANDBY 1.3 HOURS AVERAGE PROJECT DAY 10.5 hours SETUP 1.5 HOURS

18 Revision of Productivity Analysis Date Draft Dredge Pilot Value Revised Value December 5, CY/hr 73 CY/hr December 6, CY/hr 110 CY/hr December 7, CY/hr 100 CY/hr December 8, CY/hr 99 CY/hr December 10, CY/hr 110 CY/hr * Revised values based on USACE ERDC/EL TR Technical Guidelines for Environmental Dredging of Contaminated Sediments

19 Revision of Productivity Analysis Date Average Operating Production Rate Uptime Mathematical 24-hour December CY/hr 45 percent 2,200 CY December 7-8 and CY/hr 79 percent 2,500 CY

20 Revision of Resuspension Analysis

21 Revision of Resuspension M1 M2 100 meters 300 meters M6 M5 Solids and chemical monitoring i conducted at transects between Moorings 1-2 and Moorings 5-6. Boat-Based ased ADCP Monitoring Throughout Pilot Study Area

22 Dredging Resuspension Assessment is difficult due to Resuspension from Tidal Currents Upriver Tracks on December 5, 2005 during Ebb Tide

23 ADCP Profiles on December 7, 2005 during Ebb Tide Very Near-Field (<50 meters) Boat-Based Based Monitoring Can Detect Resuspension Depth (m m) TS S (mg/l)

24 ADCP Profiles on December 10, 2005 during Flood Tide Boat-Based Monitoring Demonstrates the Rapid Dispersion of Resuspension Plume Depth (m m) TSS S (mg/l)

25 Revision of Resuspension Analysis Date Production Average Very Near-Field Rate Release Rate Percent (kg/s) (kg/s) Resuspension December 5, % 5% December 6, % December 7, % December 8, % December 10, %

26 Revision of Resuspension Analysis Best Management Practices were evaluated to optimize dredging d operations while minimizing i i i resuspension. Optimize the cycle time between ee grabs by adjusting the depth of cut, the lift speed, and hang time Optimize the use of winching and cabling in place of tugboats for repositioning the rinse tank

27 Revision on Productivity Analysis Date December 5-6 Shakedown December 7-8 BMP Optimized Mathematical Uptime Resuspension 24-hour 45 percent 2,200 CY 5-6% 79 percent 2,500 CY 1-2%

28 Revision of Resuspension Release during dredging generally masked by background TSS due to movement of salt wedge and tidal resuspension. Dredge signal was detectable ONLY in very near-field (< 50 m) of dredging operation, despite wide variation in the background sediment load. Dredge signal not readily discernable at far-field of Pilot Study Area (300 meters away). No chemical signal due to dredging. Very near-field dredging release is less than 2% of solids removal under environmental dredging conditions with Best Management Practices.

29 Conclusions and Next Steps Pilot Study Report will be revised: 4,000 CY of sediment removed 9.2 hours for the work day (minus client standby time) 79% Uptime with Best Management Practice 1-2% Resuspension using Best Management Practice Additional supporting data will be added d into the report and provided as appendices Final Report anticipated June 2009